1. Field of the Invention
The present invention relates to an air-tool, and more particularly to a tool that is driven by a pneumatic actuator.
2. Description of Prior Art
In accordance with the conventional pneumatic actuator that takes compressed air as a power source, by means of a pneumatic rotary vane motor, output a twisting moment, as shown on FIG. 6, which comprises a main holder 40 having a container 41 holding a pneumatic cylinder 50, said pneumatic cylinder 50 has a chamber 52 with a rotor 60 mounted slightly off-centre, said rotor 60 is mounted on a bearing of a back cover-plate with one end, and a drive unit 70 with a spline shaft 61 to drive an output shaft drive rod 71 for connecting with variety socket heads or other tools to screw down or off bolt or to do other purposes.
Said rotor 60 of the air-tool has a symmetrical number of radial slots 62 fitted with sliding vanes 63, referring to FIG. 7, the compressed air in the main holder 40 enters the chamber 52 inside of the pneumatic cylinder 50 via inlets to push the sliding vanes 63 further to bring the rotor 60 into spinning with high-speed, by the high-speed spinning, the centrifugal force throws the vanes outward against the chamber wall so that the front face area is increased to generate the twisting power, the twisting moment is output through the spline shaft 61 to drive the drive rod 71 of the drive unit 70 output. But there are some shortcomings existing in above-mentioned conventional air-tool as follows:
1. As we know, the force of torsion on the rotor 60 has a direct relationship to the pressure of the compressed air P and the area of front face of the vanes 63, as F=P.times.A, obviously the force of the torsional force depends directly on the front face area as the area of the vane 63 extending out from the slot 62; in the still time, most of the vane 63 is hidden into the slot 62, just only a small area faces to the compressed air as primary time of starting, so the force of the twisting on the rotor 60 is not enough strong to drive the rotor rotating, hence a lag phase is often kept till the compressed air pushes almost all the vanes 63 to increase the force on the rotor 60; PA1 2. Due to the round surface of the rotor master shaft, the front face area just only is the area of the vane 63 extending out from the slot 62, so the rotor master shaft is only to increase the weight further to increase the resistance moment as starting; PA1 3. Because some viscous lubricating-oil is coated between the slots 62 and the sliding vanes 63, in the starting time, the rotor 60 rotates under a lower-speed, the centrifugal force is not enough to throw the vanes 63 outward, adding the viscosity resistance of the lubricating-oil, the sliding vanes 63 can not rapidly slide out to increase the front face area, this is a sake of causing the lag phase of running; PA1 4. For increasing the front face area to improve the outputting torsional force, some designers believe that increasing the number of the vanes 63 on the rotor 60 can solve the problem, but when the number increases over a proper amount, it not only can not obtain more twisting force, but also the vanes are unable to stand under a high torsion moment, because along with increasing the number, the width of the slot 62 and the thickness of the vane 63 are decreasing so that the intensities of the vanes 63 and the rotor 60 are reduced; PA1 5. Due to above-described increasing the number of the vanes 63, the space length between the vanes 63 is so small that the effective front face area of the vanes 63 is reduced, the output twisting moment is reduced too; PA1 6. As above-described, when the rotor 60 spins under a high-speed, the ends of the sliding vanes 63 are thrown against the chamber 52 wall by the centrifugal force, and sliding on it to wear the chamber wall under the friction; along with increasing the number of the vanes 63, the friction are increasing too, therefore the service life of the chamber 52 and the vanes 63 will be shorted relatively; PA1 7. A bit of moistness and dirty dust will be carried into the compressed air entering into the chamber 52 to heap upon the joint gap between the vanes 63 and the slot 62 over a long time so that the vanes 63 will be blocked in the slots 62.